Children with Specific Language Impairment (SLI) are known to have difficulty learning new words, which places them at greater risk for future reading impairments and academic failure. Surprisingly, there are few interventions for word learning by children with SLI that have undergone rigorous efficacy and/or effectiveness testing. The long-term goal of proposed research is to optimize an intervention with moderate to large effects on word learning by other populations of children for children with SLI. The intervention of interest is interactive book reading, where an adult uses oral reading to a child as a foundation for teaching new words. The first step towards the long-term goal is this Phase I/II Preliminary Clinical Trial, which is defined as a preliminary study addressing core design and clinical issues necessary to the future conduct of a Phase III/IV Definitive Clinical Trial that, in turn, establises the efficacy/effectiveness of the intervention. Aim 1 uses a Phase I escalation strategy to hone in on an adequate treatment intensity of interactive book reading for children with SLI. The intensities to be tested are informed by empirical word learning studies showing that children with SLI need two to three times as many exposures as their typically developing peers to learn new words. Aim 2 examines the extent of benefit associated with the adequate treatment intensity in terms of both proximal (i.e., learning the taught words) and distal outcome measures (i.e., learning beyond the taught words) and in terms of the variation in response to treatment based on pre-treatment language skills. Aim 3 is based on the idea that there are different ways of achieving the same treatment intensity. For interactive book reading, intensity is a function of the number of exposures to target words within a book (i.e., dose) and the number of exposures to target words via repeated readings of a book (i.e., dose frequency). There is strong evidence from experimental studies and theory suggesting that a regimen that maximizes dose frequency will yield better word learning outcomes than a regimen that maximizes dose, even when the overall intensity is equivalent. Aim 3 will identify the best combination of dose and dose frequency for word learning by children with SLI. The likely impact of this research is that an adequate intensity and promising dosing regimen of interactive book reading will be identified for children with SLI, for whom there are few (if any) proven treatments for word learning. Moreover, the types of outcomes that can be attained through manipulation of intensity and dosing regimen will be identified, determining whether further optimization of the treatment is needed to meet the significant word learning challenges faced by children with SLI. Lastly, the resulting findings will contribute to theories concerning the number of exemplars needed to support learning as well as theories of learning from input versus memory consolidation. Specifically, the work pushes the limits of these theories by providing evidence from children with SLI learning large numbers of words over several months, supplementing prior data from typically developing children learning small numbers of words over a few weeks.